Australia's Symbolism

Kangaroos, emus, the 6 states of Australia + territories + federation, Golden Wattles and Waratah Flowers, Black Opal gems, and the Southern Cross constellation are among the important symbols that appear regularly in Australian iconography and culture. 

The Commonwealth Coat of Arms is the formal symbol of Australia, comprised of a shield held up by a kangaroo and an emu. These animals were chosen as they are native to Australia and to symbolise the nation moving forward, as neither animal can move backward easily. 

The shield has six panels representing the six states of the country, with the border representing federation. The seven-point star above the shield represents the six Australian states with the seventh representing the territories. The floral elements framing the shield and animals are Golden Wattles, Australia's national flower.

These symbols appear again and again and again across official (and unofficial) things. For instance, a giant coat of arms adorns the rooftop of the Parliament House in the capital city of Canberra, some monetary bills and coins, inside and outside the High Court of Australia (i.e., their Supreme Court). A longstanding landmark called the Australian Heritage Hotel even serves a "coat of arms" pizza with kangaroo and emu on it.

According to the Australian National Flag Association, the large star on the bottom left-hand side of the flag is the Commonweath Star, with "six points represent[ing] the states and the seventh all the federal territories, which together constitution the nation - the Commonwealth of Australia." The five-star constellation on the right side of the flag represents the Southern Cross or Crux, symbolizing the geographical location of Australia in the southern hemisphere and relating to various indigenous legends from Aboriginal and Torres Strait Island heritage.

The crosses in the upper-left side of the flag reflect the head of state, which to date remains the Queen of England (a whole other interesting piece of Australian history, culture, and contemporary debate worth learning about). The three crosses overlaid in that part of the flag represent the principles and ideals of parliamentary democracy, the rule of law, the rights and responsibilities of citizens, and freedom of speech. 

The Aboriginal Flag, designed by Indigenous Elder Harold Thomas, symbolizes the sun (yellow), the red earth (relationship to land), and the Aboriginal people (represented by the black area of the flag). There is also an official Torres Strait Islander Flag, but I don't think I can reproduce it here due to copyright. Each state and territory also has its own flag and symbolism.

The Australian National Anthem, "Advance Australia Fair," was written in the late 1800s and was a popuar patriotic song, but didn't become the anthem until about a hundred years later. In 1984, by popular vote, it replaced "God Save the Queen" as the national anthem.